1. Field of the Invention
The present invention generally relates to new substituted ureas, to methods for preparing those substituted ureas and to agricultural uses of those substituted ureas to improve plant growth. More specifically, the present invention is directed to the reaction product formed by reacting a carboxylic acid with urea to form a new N,Nxe2x80x2-di-substituted urea, to methods for conducting that reaction and to agricultural uses of the reaction product.
2. Description of the Background
Urea, being approximately 46% by weight nitrogen, has long been preferred as a nitrogen source for fertilizing soils to stimulate plant growth. However, urea suffers from high ammonia losses when used in the presence of moisture. This disadvantage effectively restricted the use of urea for many years. It is believed that these losses are caused by the hydrolysis of urea in the presence of moisture and the enzyme urease. The addition of a water soluble salt to aqueous solutions of urea has been suggested as a means for reducing ammonia volatilization. See U.S. Pat. No. 4,500,335. While substituted ureas are also known, e.g., diphenylurea, they have found little agricultural use.
Urea undergoes condensation reactions with carboxylic acids to produce barbituates and their analogs. These products have found no agricultural uses. However, the argicutural industry has felt the need for ways to improve early seedling vigor and to increase plant biomass, both resulting in improved yield. There has been a long felt but unfulfilled need in the industry for improved methods for achieving these goals. The present invention solves those needs.
The present invention is directed to new compositions of matter comprising the reaction product of a carboxylic acid and a urea, including mono- and di-substitued ureas. The reaction product of the present invention comprises an N,Nxe2x80x2-di-substituted urea having the formula: 
where R1, R2, R3 and R4 are the same or different and are selected from the group consisting of hydrogen, substituted and unsubstituted alkyl, allyl, vinyl and alkoxyl groups having from one to six carbon atoms, substituted and unsubstituted phenyl groups and the halides.
In a preferred embodiment, the second reactant is unsubstituted urea so that R3 and R4 in the reaction product are hydrogen. In a more preferred embodiment, R1 and R2 are selected from the group consisting of hydrogen and alkyl groups having from one to three carbon atoms. Most preferably, formic acid is reacted with urea in a molar ratio of about 2:1 to produce N,Nxe2x80x2-diformylurea. While the reaction may be conducted at any temperature between about 10xc2x0 C. and about 140xc2x0 C., it is preferably conducted within the range of about 15xc2x0 C. to about 40xc2x0 C. The reaction may conveniently be conducted at room temperature. Preferably the reactants are stirred until the reaction mixture is clear. Crystals of the reaction product will form and may be separated from the reaction mixture.
The reaction products of the present invention, most preferably N,Nxe2x80x2-diformylurea has been found to produce enhanced growth in plants when used in a variety of ways. These reaction products, most preferably diformylurea, produce enhanced growth when applied to seeds prior to planting, when applied to the soil surrounding the plant at or after planting or when applied to the foliage of the plant, e.g., at the three leaf stage of growth. An aqueous solution containing from about 0.001-1.0 M of the reaction product may be applied to the surface of seeds at a rate of about 15-750 ml. of solution per 100 lbs of seed. In a convenient method, the solution may be applied to the surface of the seeds or the seeds may be soaked in such a solution for about 2-24 hours, preferably for about 24 hours, prior to planting. Alternatively, such a solution may be applied to the soil surrounding the seed and/or emerging plant. When so applied, it is suggested that the solution be applied at a rate of about 1-100 grams of diformylurea or other reaction product per acre. Still another alternative is the application of such an aqueous solution to the foliage of the plant, preferably at the three leaf growth stage, at a rate of about 1-100 grams of diformylurea or other reaction product per acre. When applied to the foliage, those skilled in the art may include a conventional vegetable oil and surfactant in the solution to improve the retention of reaction product on the leaves so that it may be more readily absorbed by the plant.
The newly discovered reaction products of urea and carboxylic acids described herein, particularly N,Nxe2x80x2-diformylurea, have produced significantly improved growth when applied to the seeds and foliage of a variety of agricultural products. Accordingly, it is believed that a significant improvement in crop development may be obtained using these new products. These and other meritorious features and advantages of the present invention will be more fully appreciated from the following detailed description and claims.